A class of machines exists in the art generally known as “scroll” machines for the displacement of various types of fluids. Such machines may be configured as an expander, a displacement engine, a pump, a compressor, etc., and the features of the present invention are applicable to any one of these machines. For purposes of illustration, however, the disclosed embodiments are in the form of a hermetic refrigerant compressor.
Generally speaking, a scroll machine comprises two spiral scroll wraps of similar configuration, each mounted on a separate end plate to define a scroll member. The two scroll members are interfitted together with one of the scroll wraps being rotationally displaced 180° from the other. The machine operates by orbiting one scroll member (the “orbiting scroll”) with respect to the other scroll member (the “fixed scroll” or “non-orbiting scroll”) to make moving line contacts between the flanks of the respective wraps, defining moving isolated crescent-shaped pockets of fluid. The spirals are commonly formed as involutes of a circle, and ideally there is no relative rotation between the scroll members during operation; i.e., the motion is purely curvilinear translation (i.e., no rotation of any line in the body). The fluid pockets carry the fluid to be handled from a first zone in the scroll machine where a fluid inlet is provided, to a second zone in the machine where a fluid outlet is provided. The volume of a sealed pocket changes as it moves from the first zone to the second zone. At any one instant in time there will be at least one pair of sealed pockets; and where there are several pairs of sealed pockets at one time, each pair will have different volumes. In a compressor, the second zone is at a higher pressure than the first zone and is physically located centrally in the machine, the first zone being located at the outer periphery of the machine.
Two types of contacts define the fluid pockets formed between the scroll members, axially extending tangential line contacts between the spiral faces or flanks of the wraps caused by radial forces (“flank sealing”), and area contacts caused by axial forces between the plane edge surfaces (the “tips”) of each wrap and the opposite end plate (“tip sealing”). For high efficiency, good sealing must be achieved for both types of contacts.
One of the difficult areas of design in a scroll-type machine concerns the technique used to achieve tip sealing under all operating conditions, and also at all speeds in a variable speed machine. Conventionally, this has been accomplished by (1) using extremely accurate and very expensive machining techniques, (2) providing the wrap tips with spiral tip seals, which, unfortunately, are hard to assemble and often unreliable, or (3) applying an axially restoring force by axial biasing the orbiting scroll or the non-orbiting scroll towards the opposing scroll using compressed working fluid.
The utilization of an axial restoring force first requires one of the two scroll members to be mounted for axial movement with respect to the other scroll member. This can be accomplished by securing the non-orbiting scroll member to a main bearing housing by means of a plurality of bolts and a plurality of sleeve guides as disclosed in Assignee's U.S. Pat. No. 5,407,335, the disclosure of which is hereby incorporated herein by reference. Second, a biasing load needs to be applied to the axially movable non-orbiting scroll to urge the non-orbiting scroll into engagement with the orbiting scroll. This can be accomplished by forming a chamber on the side of the non-orbiting scroll opposite to the orbiting scroll member, placing a floating seal in the chamber and then supplying a pressurized fluid to this chamber. The source of the pressurized fluid can be the scroll compressor itself. This type of biasing system is also disclosed in the aforementioned U.S. Pat. No. 5,407,335.
The floating seal is a well-known component of a pressure balanced axially compliant scroll compressor design. The floating seal assembly functions as a valve to enable or prevent the flow of high-pressure refrigerant gas from the discharge area of the compressor to the suction area of the compressor. At normal compressor operating conditions, the valve is closed and a face seal prevents the bypass of gas from discharge to suction. The valve opens in response to a high discharge-to-suction pressure ratio in the compressor. This characteristic is beneficial in system failure modes that tend to create a potentially damaging vacuum condition in the suction area of the compressor.
The prior art floating seal is an assembly of two metal plates and two polymer seals. The lower plate is an as-cast aluminum part with vertical posts that fit through holes in the upper cast iron plate. The upper plate has a feature incorporated into its top surface that acts as a face seal with the muffler plate whenever the two components are in contact. The two polymer seals are located by and held between the two plates. The assembly process for the prior art floating seal involves stacking the pieces together and then plastically deforming the aluminum posts such that the top ends locally spread out over the iron plate to form a rigid attachment.
The present invention provides the art with an improved floating seal design which is a single plate. The single plate design retains the functionality of the prior art design while eliminating the lower plate and the swaging portion of the assembly. In addition, the finish machining of the plate is simplified to become a single set-up operation without the need for equipment to drill holes in the upper plate. In one embodiment, the floating seal utilizes a U-shaped seal. In another embodiment the floating seal utilizes an L-shaped seal. In yet another embodiment, the floating seal utilizes flip seals.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.